Coded track circuit signaling system



Feb. 10, 1942. PH|NNEY 2,272,581

CODED TRACK CIRCUIT SIGNALING SYSTEM Filed Oct. 24, 1940 3 Sheets-Sheet1 Fla 1.

SY 52 re; &

-12esponds to1000-only rp qi F lyqu 5 Gen. INVENTOR =="OC1-2 fi 0C BY JT 6 Tr 72M 1 5 1942. R. M. PHINNEY 72,581

CODED TRACK CIRCUIT SIGNALING SYSTEM I Filed Oct. 24, 1940 3Sheets-Sheet 2 FIG. 2.

I! 3' Responds to IOOO'YOnIy 54 %VENTOR 60-AC intermittentlySuperimposed BY y by 1000-potential NW Feb. 10, 1942. R. M. PHINNEY2,272,581

CODED TRACK CIRCUIT SIGNALING SYSTEM Filed Oct. 24, 1940 3 Sheets-Sheet5 MCMJFJ Uyq fi i I 4 s v W" !%1 i I fjlaofL 3 IL cM5-6 mvENTop 60-ACintermittently Superimposed I by 1000- potential ATTORNEY Patented Feb.10, 1942 r'rs rsr cries CODE!) TRACK CIRCUIT SIGNALING SYSTEM Robert M.Phinney, Rochester, N. Y., assignor to General Railway Signal Company,Rochester,

29 Claims.

The present invention relates to signaling systems of theabsolute-permissive-block type and more particularly to a double orduplex coded track circuit for such systems.

By coded track circuit is meant a track circuit of the coded typewherein impulses of current are repeatedly applied to one end of thetrack circuit and suitable code responsive apparatus detects the code atthe other end of such track circuit. By a double coded track circuit ora duplex coded track circuit is meant a track circuit in which codes maybe applied at both ends and code responsive apparatus may be connectedat both ends wherein each code responsive apparatus only responds to thecodes applied by the code applying apparatus at the other end of thetrack circuit.

In order to control a signal in accordance with trailic conditions inone or more blocks in advance without the requirement of signal controlline wires it is desirable to have the track relay or the coderesponsive apparatus located adjacent the signal, namely, at theentrance end of the track section. Obviously, if traffic moves in bothdirections as is often the case for single track railroads, in whichcase there may be a signal at each end of such track section forgoverning traffic into the section, it becomes apparent that it isdesirable to have a track relay or code responsive means at each end ofthe track section, which may be shunted out by a train in that sectionand if not shunted refleets trafiic conditions in advance. Since trafficconditions in opposite directions of such section may be different thecodes transmitted in opposite direction may be different. Also whencontinuous inductive train control is employed it is found necessary toapply the code to the exit end of the section so that it may be detectedin front of the train and for single track railroads both ends of eachsection are at times exit ends. These characteristics of a track circuitare desirable in order to avoid the need of line wires between thesignal and the track relay or code responsive apparatus controllingthesame. In

view of these facts it is desirable to employ a double track circuit, soto speak, in which there is a track relay or code responsive means ateach end controlled by energy applied to the opposite end.

In accordance with the present invention it is proposed to constructsuch a double track circuit by providing each end of a track sectionwith synchronously operated contacts which simultaneously connect codecreating apparatus to one end of the track circuit while code responsiveapparatus is connected to the other end of the track circuit and viceversa. By reason of the fact that the code which is to be applied to oneend of a track section may be different than the code applied to theopposite end of the track section it is not possible to alternate theuse of the track rails to the two track circuits, once for each codeelement, because if this were done the code element spacing of the codestransmitted in opposite directions through the track would notsynchronize when difierent rate codes are applied at opposite ends. Inview of this fact, and in accordance with the present invention, it isproposed to alternately allow the use of the track rails of a tracksection for its two track circuits for time periods long enough totrans-' mit suificient elements of the rate codes transmitted to makeinterpretation possible. In other words, it is proposed to allow a codeto be transmitted in one direction along the track section long enoughto have its code responsive apparatus respond and to thereafter allowthe transmission of a code in the opposite direction through the railsof the track section for a period long enough for its code responsiveapparatus to respond and to employ code responsive apparatus which willmanifest the reception of a continuous code in spite of the fact thatthe code is intermittently interrupted during the time when a code isbeing transmitted in the opposite direction.

Another object of the present invention resides in the provision ofcontacts at each end of each track circuit for alternately connectingthe code creating apparatus and the code responsive apparatus to thetrack rails, and to provide means for operating the contacts at oppositeends of the track section in synchronism. More specifically it isproposed to operate these contacts by electro-responsive means connectedthrough a suitable filtering means to a transmission line upon which issuperimposed a special current which is intermittently applied for timeintervals long enough to transmit a code through the rails of a tracksection and which is then removed for substantially the same timeinterval.

Other objects, purposes and characteristic features of the presentinvention will in part be described hereinaiter and will in part appearfrom the accompanying drawings, in which:

Figs. 1,2 and 3 when laid end-to-end constitute a portion of an absolutepermissive block system embodying the present invention.

Referring to the drawings the track rails I have been shown divided byinsulating joints 2 into track sections of which the sections X and Yand the adjacent ends of sections W and Z only have been shown. Asillustrated the entrance end for eastbound trafiic to the blocks orsections X, Y and Z have been provided with signals S2, S4 and S6respectively, and similarly the entrance end for west-bound traflic tothe blocks Y, X and W have been provided with signals S5, S3 and SI,respectively. These signals S may be of any suitable construction suchas semaphore signals, search-light signals, or multi-aspect signals andfor convenience only multi-aspect signals each having a green lamp 9, ayellow lamp y, and a red lamp 1 have been illustrated. The green lampsignifies clear, the yellow lamp caution and the red lamp signifiesdanger traffic conditions ahead, when lighted.

Parallel to the railway track is preferably provided a transmission lineTr which supplies the necessary power for charging storage batteries,for operating code creating apparatus and for applying energy to thetrack rails. This transmission line preferably supplies power ofcommercial frequency such as current of 60 cycles per second. This 60cycle current has preferably superimposed thereon a high frequencycurrent, such as current of 1000 cycles per second, this high frequencycurrent being applied intermittently for, say, two second intervalsspaced by a period of two second intervals.

This intermittently applied high frequency cur rent is preferablyderived from a suitable generator Gen and is preferably intermittentlyap plied by suitable circuit interrupting means such as the contact 5intermittently closed by a cam 6 which may be driven by a suitablemotor, such as a synchronous motor operated from the 60 cycle source ofcurrent supply. In order to prevent the 60 cycle energy from flowingthrough the winding of the generator Gen a condenser C is preferablyemployed. At each track section junction there is provided asynchronizing relay SY which is connected to be responsive to thesuperimposed high frequency current, the circuit for each of theserelays SY preferably having included in series therewith a condensersuch as the condenser OCl-2 shown for the junction provided with signalsSi and S2. This condenser is preferably of such a capacity that incombination with the inductance of the relay SY the circuit therethroughis tuned for the high frequency current.

Each track section junction is also preferably provided with a codingmotor CM, the coding motor for the location of signals SI and S2 havingbeen designated CMI--2. These coding mo tors CM are provided with codingcontacts designated l and E80 and closed 75 and 180 times per minute,respectively, although coding contacts operating at other frequenciessuch as contacts which close 120 times a minute may be employed ifdesired.

Since the apparatus and wiring for the various signals is identical itis deemed sufficient to describe the apparatus associated with thesignal S2 and to designate like parts of all other signals with likereference characters having distinctive suffixes and exponentscorresponding to the sufiix of the associated signal.

Referring to the signal S2 and its associated apparatus located at theentrance end to the block X, this signal S2 is'controlled through themedium of code following relays CLZand CA2 as is readily apparent fromthe circuits for the signal lamps g, y and r for the signal S2 includingcontacts 35 and 36 During the periods of energization of thesynchronizing relay SY the rails of the west end of the block X areconnected to the secondary winding of the transformer TTZ. Thistransformer has its primary winding normally (under clear trafficconditions) connected to the transmission line Tr through a circuitincluding the front contact I0 of the track repeater relay TRI, thecontact lSEl of the coder CMl--2, back contact H of the directionalstick relay SRI and through back contact I2 of the directional stickrelay SR2. Under caution traffic conditions for west-bcund traffic inblock X this transformer TTZ is connected to the transmission line T1-through the back contact I0 of the track repeater relay TRI, throughcoding contact 15, through the front contact H of the directional stickrelay SR9 and through back contact l2 of the directional stick relaySR2. When however the synchronizing relay SY is deenergized the west endof the track section X has its track rails connected to the track relayT2.

Intermittent picking up of the track relay T2 in response to either a 75impulse per minute code or a 180 impulse per minute code will cause itscontact M to intermittently connect the posi tive terminal of a battery(conventionally represented by the terminals and to opposite ends of theprimary winding of the transformer T82, which primary winding has itsmid-point connected to the terminal of the same battery. Thistransformer is therefore in effect energized by alternating current of'75 or 180 cycles per minute, as the case may be. One secondary windingof this transformer TS2 has its midpoint connected to one terminal ofthe relay CA2 and has the two ends of its winding connected to thestationary front contact and the stationary back contact, respectively,associated with the movable contact I5 of the relay T2, so that thiscontact I5 constitutes a rectifying contact for the alternating currentinduced in this secondary winding of the transformer TS2. Thetransformer TS2 is provided with another secondary winding which isconnected through a condenser lC2 to a full-wave rectifier REE which hasits out-put direct current terminals connected to the clear relay CL2.The condenser |C2 is of such capacity as compared with the inductance inits circuit so as to resonate the circuit at a frequency of 180 cyclesper minute, so that the relay CL2 will only pick up when a code of 180cycles or impulses per minute is received by the track relay T2 and willnot pick up if a code of either 75 or impulses per minute is received.As heretofore pointed out the synchronizing relay SY is energized forsubstantially a two second interval and is then deenergized forsubstantially a two second interval.

In order to be assured that the clear relay GL2 or the caution relay CA2will remain energized during the two second off period intervals theserelays CL2 and CA2 have been provided with stick circuits. These stickcircuits for relays CLZ and CA2 include stick contacts [l and I8respectively, which are included in series with condensers 2G2 and 302,respectively, through front contacts I9 and 20 respectively, of therelay SY during the .off code period. These condensers 2C2 and 302 arecharged from a battery B2 through back contacts l9 and 20 respectively,when the relay SY is deenergized and are connected to the stick windingsof the relays CLZ and CA2 when the relay SY is energized, so that adefinite amount of energy is transferred from the battery B2 to anenergized relay for each code transmitting period.

The track repeater relay TRZ is a slow dropping relay and may beenergized through two circuits, one of which includes the front contact22 of the relay CA2 and the other of which includes a front contact 23of the relay GL2. Each of the signals S is provided with a directionalstick relay of which the directional stick relay for the signal S2 hasbeen designated SR2. This directional stick relay SR2 may be picked upby a circuit including the back contact 25 of the track repeater relayTRI, back contact 2'5 of the relay GL2, back contact 21 of the relayCA2, front contact 28 of the relay TRZ. This stick relay SR2 when onceenergized may be maintained energized through a stick circuit includingthe back contact BI of the relay GL2, back contact 32 of the relay CA2,and front stick contact 33 of. this directional stick relay SR2. Thereis also an auxiliary stick circuit for this relay including the backcontact 3& of slow dropping track repeater relay TR2.

Operation Let us first assume that all of the signals governingeast-bound trailic are in their normal clear traffic condition in whichtheir green lamps g, are energized and that there is an east-bound trainwhich just entered the block W. Since this east-bound train entirelyshunts the track relay Tl the caution relay CA! and the clear relay CL!as well as the track repeater relay TRI will all assume theirdeenergized position. Also the back contact 215 of the relay TR2 is openas a result of which the directional stick relay SRI did not pick up inresponse to closure of back contacts 26 and 21 Under this conditionsince the contacts N3 of the relay TR! and contact I I of the relay SR!are both in their retracted position the transformer TT2 is entirelydeenergized, because its two energizing circuits including the codingcontacts 15 and H39, respectively, of the coding motor ClVll2 are open.This results in the signal S3 at the east end of the block X andgoverning west-bound trafiic assuming the stop position. Similarly,since the relays SR3, TRB, CA3 and CLS also all assume their deenergizedposition no coded current can be applied to the west end of the block Yand accordingly the signal S5 at the east end of this block Y andgoverning west-bound traffic will also assume its stop position. It is,of course, understood that the signal Si no longer assumes its clearcondition because the relay CM is deenergized, the track relay Tl beingshunted by the train occupying the block W, and since the green lamp gof the signal SI includes the front contact 35 this green lamp g will ofcourse be extinguished. Also, since the lamp y for the signal SIincludes a front contact 36 of relay CAI this lamp y will also beextinguished. The lamp r of this signal S! will be energized through acircuit including these back contacts 35 and'36 It is thus seen that theusual tumble down of track circuits is eifected upon entrance of a trainresulting in all opposing signals in the single track section being putto stop.

The train under consideration may of course proceed, at speed, into theblock X because signal S2 is clear and has its green lamp g energized.This green lamp g for signal 2 isenergized, as indicated in thedrawings, because its associated clear relay 0L2 is in its energizedposition. This, relay CL is in its energized condition becauseintermittently for two seconds at a time, spaced by two secondintervals, the track relay T2 is energized at a coding rate of 1'80impulses per minute. These.- intermittent energ-izations of the trackrelay T2 occur when: the synchronizing relay SY is deenergized. Sincethese intermittent energizations cause the contact It? to apply 180cycle per minute. current to thetransformer TS2 for which the inputcircult for the rectifier REZ is tuned sufficientcurrent will be.supplied by this rectifier to pick upv the relay GL2. energizedcondition and its stick circuit includ-= ing its stick" contact [1closed, the lower winding of the relay GL2. is energized by the currentswhich were stored in the condenser 202 during the period of.deenergization of the synchronizing relay SY and which current isapplied to this winding during the period of deenergization of its upperwinding.

The caution relay CA2 is also energized under this condition but this isof no importance since the circuit for the clear lamp G does not includea contact of the caution relay CA2. east-bound train moving in the blockW the track repeater TRI is deenergized but this is of no importance atthe present time insofar as the pickup circuit for the directional stickrelay SR2 is concerned because its pick-up circuit is open at backcontacts 26 and 21 of relays CLZ and CA2, respectively. As the train inquestion however passes the signal S2 and enters the block X the trackrelay T2 will remain continuously deenergized thereby resulting in thedeenergization and dropping of the relays CLZ and CA2. With the relaysGL2 and CA2 both in their retracted posi-' tion the signal S2, forreasons heretofore given, indicates danger. With both of these relaysGL2 and CA2 deenergized, and with the track repeater relay TRI' alsodeenergized, for reasons heretofore given, a pick-up circuit for thedirectional stick relay SR2 is closed through back contacts of theserelays TRI, GL2 and CA2 and front contact 28 of the track repeater relayTRZ. This track repeater relay TR2 is sufficiently slow dropping toallow the directional stick relay SR2 to pick up before its contact 23is opened. As soon as the directional stick relay SR2 has assumed itspicked up position a stick circuit for this directional stick relay SR2is closed which includes the back contacts 31 and 32 of the relays CL2and CA2, respectively, and also includes the stick contact 33 of therelay SR2. Upon dropping of' the repeater track relay TRZ a second stickcircuit is closed for the directional stick relay SR2 which includes theback contact 34 of this relay TRZ. As soon as the train has fully leftthe block W the code following relay CAI and CLI, as well as therepeater track relay TRI, will again be energized. The picking up of thetrack repeater re lay TR! opens its back contact 25 so that thepick-upcircuit for the relay SR2 is now broken. It should be rememberedthat with relay TR2 assuming its retracted position and the relay SR2assuming its energized position a 75 impulse per minute code is appliedto the east end of block W, so that the signal at the entrance end (westend) of the block W indicates caution, as illustrated for the signal S4in the drawings. apparatus associated with the signalS2 is now in Withthe clear relay GL2- in its.

With the The the same condition as that illustrated for the signal S6 inthe drawings.

As the train passes the signal S4 the same operations, as just explainedfor the signal S2 when the train passed the signal S2, take place. Thatis, the signal S4 is operated to its stop condition and the directionalstick relay SR4 is picked up and stuck up. As the train in question nowpasses entirely out of the block X the relays CA2 and TRZ pick up andthereby open the pickup circuit and both stick circuits for thedirectional stick relay SR2. The Picking up of caution relay CA2 (relayCL2 still down) closes an energizing circuit for the yellow lamp Y ofthe signal S2. The dropping of the directional stick relay SR2 (relayTRZ being up) causes the entering signal (not shown) at the west end ofthe block W to give a clear indication.

Similar operations take place when the train under consideration passesthe signal S6.

Let us now assume that the train in question has passed entirely throughthe blocks X and Y and is now occupying the block Z. Under thiscondition the apparatus is in the condition as illustrated in thedrawings. It will be noted that with the directional stick relay SR6energized by its stick circuit that its contacts II and I2 will be intheir raised condition. Under this condition the transformer TTG will bedeenergized, whereas the transformer TT5 will be energized by currentcoded at the 75 impulse per minute rate. The circuit for the winding ofthe transformer TT5 may be traced as follows: starting at the oneterminal of the transmission line Tr through the winding of thetransformer TT5, back contact 12 of the relay SR5, front contact I l ofthe directional stick relay SRt, coding contact 15 of the coding motorCM56, back contact it of the track repeater relay TRB, to the other wireofthe transmission line Tr. This application of the 75 impuls per minuterate code to the east end of the track section Y causes the track relayT4 at the west end of this section Y to be intermittently picked up atthe 75 impulse per minute code rate for substantially two seconds, afterwhich the track relay T4 remains deenergized for substantially twoseconds. This intermittent picking up of the track relay T4 at the 75per minute impulse code rate for alternate two second periods causes therelay CA4 to pick up but does not allow sufficient current to flow tothe clear relay CL l through the medium of the rectifier RE4 so thatthis clear relay GL4 remains deenergized. The caution relay CA4 will,however, be picked up by this '75 impulse per minute code rate, eventhough only applied intermittently, as

a result of which the caution lamp y for the signal 4 will be energizedthrough back contact 35 of the relay CM and front contact 36 of therelay CA4. The picking up of the caution relay CA4 following unoccupancyof block Y caused the stick circuit for the relay SR4 (which was closedduring the occupancy of the block Y) to be broken. Also with the cautionrelay CA4 in its energized condition even though the clear relay GL4 isin its deenergized condition will cause energization of the trackrepeater relay TBA, thereby causing the 180 impulse per minute code ratecircuit for the transformer TT3 to be closed, this circuit including theback contact I2 of the relay SR3, back contact H of the relay SR4, the180 impulse per minute coding contact of the coder CM3 l and the frontcontact Ill of the relay TR4. It is thus seen that the block X isprovided at the east end with coded energy of the 180 impulse per minutecoding rate as a result of which the signal S2 will again assume itsclear condition.

Since the coding impulses of current flowing in the track railsconstitute alternating current they can be inductively detected on thelocomotive, as for instance, through the medium of receivers RI onelocated over each track rail and supported in front of the locomotive.These receivers comprise a core of laminated iron on which there iswound a coil. These coils are connected in series and to an amplifier Aand also include in series therewith a condenser C which tunes thiscircuit to the frequency of the alternating current flowing in the trackcircuit cycle in this instance). The output side of this amplifier Afeeds current of amplified quantity to the code following relay CR sothat this code following relay CR follows the code pulses in the trackrails in the same Way as the track relay of the block occupied by thetrain would have done had the train not entered the block. This codefollowing relay CR controls the carcarried signals 9, y and r in exactlythe same way and by similar apparatus as that employed to control thewayside signals. For this reason like parts have been designated by likereference characters except that exponents or suffixes t have beensubstituted for the numeral exponents and sufiixes. There is, however,one difference between the car-carried apparatus and the trackwayapparatus in that the stick circuits of the relays CA and CL employedalong the trackway have been omitted from corresponding relays carriedon the locomotive. It will be remembered that stick circuits wereemployed to hold these relays CA and CL energized during the periodswhen the alternate track circuit is in use. In order to prevent thecar-carried relays CM and CRt from dropping during this period, theserelays CLt and CM have been made specially slow dropping.

Although no brake control apparatus or other means for retarding thespeed of the train have been illustrated, it should be understood thatsuitable automatic brake control apparatus controlled by the car-carriedrelays CM and CM may be employed, if desired.

The applicant has thus disclosed an absolutepermissible-block signalingsystem for railroads capable of operating either wayside or cab signalsand which does not require any line wires except the usual powertransmission line along the trackway, and which employs double orduplicate track circuits, one track circuit having a track relay at oneend of the block and the other track circuit having a track relay at theother end of the same block. In each block, track circuits are madeavailable alternately by durations of time sufficiently along to allowan entire code to be transmitted and received. Although the applicanthas disclosed only one specific embodiment of the present invention, itshould be understood that this has been done only for the purpose ofdisclosing the nature of the invention by illustrating one specific formthereof, and should not be construed to limit the number of embodimentsin which the invention may take form, and it should be understood thatvarious changes, modifications, and additions may be made to adapt theinvention to the particular problems encountered in practicing the sameand without departing from the spirit or scope of the invention exceptas required by the scope of the following claims.

What I claim as new is:

1.- In a duplex track circuit of the coded type comprising, a section oftrack, code applying apparatus at each end of said section, coderesponsive apparatus at each end of said section, and double throwcontacts at each end of said section operating in synchronism to connectthe code applying apparatus at one end to the code responsive apparatusat the other end through the rails of said section and connect the codeapplying apparatus at the other end to the code responsive apparatus atsaid one end through the rails of said section alternately, said doublethrow contacts assuming alternate positions at such a slow rate that acomplete code comprising a plurality of impulses may be transmitted inopposite directions through the rails of said section during such singlealternate connection by said double throw contacts.

2. In a duplex track circuit of the coded type comprising, a section oftrack, code applying apparatus at each end of said section, coderesponsive apparatus at each end of said section, and double throwcontacts at each end of said section operating in synchronism to connectthe ternately in opposite directions through the rails of said sectionduring each alternate connection, and said code responsive apparatushaving slow acting operating characteristics such as to manifest acontinuous code in spite of its intermittent interruption due to suchalternation.

3. In combination, a track section separated by insulating joints fromthe adjacent track, code creating apparatus and code responsiveapparatus at each end of said sections, double throw contacts at eachend of said section operated substantially in synchronism, and circuitwires including said contacts to alternately connect the code creatingand code responsive apparatuses to the ends of said section in such amanner that the code creating apparatus at one end is connected to thetrack section when the code responsive apparatus at the other end isconnected to the track section, the timing of said contacts being suchthat a complete code consisting of a plurality of current impulses istransmitted first from one end to the other and then from the other tosaid one end of said track section.

4. In combination, a track section separated by insulating joints fromthe adjacent track, code creating apparatus and code responsiveapparatus at each end of said sections, double throw contacts at eachend of said section operated substantially in synchronism, and circuitwires to alternately connect the code creating and code responsiveapparatuses to the ends of section,

apparatus being so constructed that it will manifest continuousreception of a code in spite of e the interruption during which a codeconsisting of a plurality of current impulses is being transmitted tothe opposite end.

5. In combination, a railway track divided into sections by insulatingjoints, a transmission line extending along said railway track, codecreating apparatus and code responsive apparatus at each end of eachtrack section,contacts at each end of each track section for alternatelyconnecting said code creating and said code responsive apparatus to therails of such track a distinctive current intermittently superimposedupon the transmission current of said transmission line, andelectro-responsive means controlled by said intermittently superimposedcurrent for intermittently closing said contacts in such a manner thatthe code creating apparatus is connected to a particular end of eachtrack section while the code responsive apparatus is connected to theopposite end of such track section for a time during which a completecode consisting of a plurality of current impulses is transmitted and sothat the code responsive apparatus is connected to said particular endof each track section while the code creating means is connected to theOpposite end of such track section for a time during which a completecode consisting of a plurality of current impulses is transmitted.

6. In combination, a railway track divided into sections by insulatingjoints, a transmission line extending along said railway track, codecreating apparatus and code responsive apparatus at each end of eachtrack section, contacts at each end of each track section foralternately conmeeting said code creating and said code responsiveapparatus to the rails of such track section, a distinctive currentintermittently superimposed upon the transmission current of saidtransmission line, and electro-responsive means controlled by saidintermittently applied distinctive current for intermittently closingsaid contacts in such a manner that the code creating apparatus isconnected to a particular end of each track section while the coderesponsive apparatus is connected to the opposite end of such tracksection and so that the code responsive apparatus is connected to saidparticular end of each track section while the code creating means isconnected to the opposite end of such track section said intermittentlyapplied distinctive current being applied and removed for sufiicientlylong time periods to allow a complete code consisting of a plurality ofimpulses to be sent in opposite directions alternately.

'7. In combination, a railway track divided into sections by insulatingjoints, a transmission line extending along said railway track, codecreating apparatus and code responsive apparatus at each end of eachtrack section, contacts at each end for intermittently closing saidcontacts in such a manner that the code creating apparatus is connectedto a particular end of each track section while the code responsiveapparatus is connected to the opposite end of such track section andsothat the code responsive apparatus is connected to said particular endof each track section while the code creating means is connected to theopposite end of such track section said intermittently applieddistinctive current being applied and removed for sufficiently long timeperiods to allow a complete code comprising a plurality of code elementsto be sent in opposite directions alternately and said code responsiveapparatus being constructed to manifest the continuous reception of acode in spite of its intermittent nature.

8. In a duplex track circuit of the coded type comprising, a section oftrack, code applying apparatus at each end of said section, coderesponsive apparatus at each end of said section, and double throwcontacts at each end of said section operating in synchronism to connectthe code applying apparatus at one end to the code responsive apparatusat the other end through the rails of said section and connect the codeapplying apparatus to the other end to the code responsive apparatus atsaid one end through the rails of said section alternately, said doublethrow contacts assuming alternate positions at such a slow rate thatcomplete codes each comprising a plurality of impulses will betransmitted alternately in opposite directions through the rails of saidsection during such connection.

9. In a duplex track circuit of the coded type comprising, a section oftrack, code applying apparatus at each end of said section, coderesponsive apparatus at each end of said section responsivedistinctively to different codes each consisting of a plurality ofimpulses, and double throw contacts at each end of said sectionoperating in synchronism to connect the code applying apparatus at oneend to the code responsive apparatus at said one end through the railsof said section and connect the code applying apparatus at the other endto the code responsive apparatus at said one, end through the rails ofsaid section alternately, said double throw contacts assuming alternateposition at such a slow rate that a complete code comprising a pluralityof impulses may be transmitted alternately in opposite directionsthrough the rails of said section during such connections maderepeatedly, and said code responsive apparatus having slow actingoperating characteristics such as to manifest a continuous code in spiteof its intermittent interruption due to such alternation.

'10. In combination, a railway track divided into sections by insulatingjoints, a transmission line extending along said railway track, codecreating apparatus and code responsive apparatus at each end of eachtrack section, contacts at each end of each track section foralternately connecting said code creating and said code responsiveapparatus at that end to the rails of such track section, a distinctivecurrent intermittently superimposed upon the transmission current ofsaid transmission line, and electroresponsive means controlled by saidintermittently applied distinctive current for intermittently closingsaid contacts in such a manner that the code creating apparatus isconnected to a particular end of each track section while the coderesponsive apparatus is connected to the opposite end of such tracksection and so that the code responsive apparatus is connected to saidparticular end of each track section while the code creating means isconnected to the opposite end of such track section said intermittentlyapplied current being applied and removed for sufficiently long timeperiods to allow a complete code consisting of a plurality of impulsesto be sent first in one direction and then in an opposite directionthrough the track section.

11. In combination, a railway track divided into sections by insulatingjoints, a transmission lineextending along said railway track, codecreating apparatus and code responsive apparatus at each end of eachtrack section, said code creating apparatus creating one of twodistnctive kinds of codes each comprising a plurality of impulsesdistinctive in character and said code responsive apparatus manifestingwhich of the two distinctive codes is being received, contacts at eachend of each track section for alte nately connecting said code creatingand said code responsive apparatus to the rails of such track section, adistinctive current intermittently superimposed upon the transmissioncurrent of said transmission line, and electro-responsive meanscontrolled by said intermittently applied current for intermittentlyclosing said contacts in such a manner that the code creating apparatusis connected to a particular end of each track section while the coderesponsive apparatus is connected to the opposite end of such tracksection and so that the code responsive apparatus is connected to saidparticular end of each track section while the code creating means isconnected to the opposite end of such track section said intermittentlyapplied distinctive current being applied and removed for sufiicientlylong time periods to allow a complete code consisting of a plurality ofimpulses to be sent in opposite directions alternately and said coderesponsive apparatus being constructed to manifest the continuousreoeption of a code in spite of its intermittent nature.

12. In an absolute-permissive-block signaling system, the combinationwith a railway track divided into blocks by insulating joints, a signalat each end of each block to govern the movement of trafiic into suchblock from that end, code responsive means associated with each signaland controlling the same and governed through the rails of the block inadvance by code creating means located at the exit end of such block,and synchronously operated contacts at opposite ends of each block foralternately connecting the code creating means and the code responsivemeans across the rails at such end of the block in such synchronousrelation with the operation of the contacts at the opposite end of theblock that the code responsive means at the two ends of the block arealternately controlled by the code creating means at the opposite end ofthe block, said contacts operating at a sulficiently slow rate to allowcomplete codes each consisting of a plurality of code elements to besent alternately in opposite directions through the rails of such blockto control the code responsive means at the ends of the block.

13. In an absolute-permissive-blocl: signaling system, the combinationwith a railway track divided into blocks by insulating joints, a signalat each end of each block to govern the movement of traffic into suchblock from that end, code responsive means associated with each signaland controlling such signal and governed through the rails of the blockin advance by code creating means located at the exit end of such block,and synchronously operated contacts at opposite ends of each block foralternately connecting the code creating means and the code responsivemeans across the rails at such end of the block in such synchronousrelation with the operation of the contacts at the opposite end of theblock that the code responsive means at the two ends of the block arealternately controlled by the code creating means at the opposite end ofthe block, said contacts operating at a sufiiciently slow rate to allowcomplete codes each consisting of a plurality of current impulses to besent alternately in opposite directions through the rails of such block,and said code responsive means being constructed to manifest thecontinuous reception of a code in spite of its intermittent reception.

14. In an absolute-permissive-blocl; cab signaling system, thecombination with a railway track divided by insulating joints intoblocks,

code responsive means at each end of each block governed through therails of such block by code creating means located at the opposite endof the block, synchronously operated contacts at the two ends of eachblock for alternately connecting the code creating means and the coderesponsive means across the rails at its end of the block in suchsynchronous relation with the operation of the contacts at the oppositeend of the block that the code responsive means at the two ends of theblock are alternately controlled by the code creating means at theopposite end of the block, said contacts operating sufficiently slow toallow a complete code consisting of a plurality of current impulses tobe transmitted during each closure of such contacts, means forcontrolling each code creating means by the code responsive means at theadjacent end of the block next in advance, and car-carried apparatusincluding a cab signal controlled by the coded current flowing in thetrack rails in advance of the vehicle carrying such car-carriedapparatus.

15. In absolute-permissive-block cab signaling system, the combinationwith a railway track divided by insulating joints into blocks, coderesponsive means at each end of each block governed through the rails ofsuch block by code creating means located at the oppoposite end of theblock, said code responsive means being constructed to continuouslymanifest a code even though the code is intermittently absent for a timeperiod to allow a complete code comprising a plurality of currentimpulses to be transmitted in the opposite direction, synchronouslyoperated contacts at the two ends of each block for alternatelyconnecting the code creating means and the code responsive means acrossthe rails at its end of the block in such synchronous relation with theoperation of the contacts at the opposite end of the block that the coderesponsive means at the two ends of the block are alternately controlledby the code creating means at the opposite end of the block, saidcontacts operating sufficiently flow to allow a com plete codecomprising a plurality of current impulses to be transmitted during eachclosure of such contacts, means for controlling each code creating meansby the code responsive means at the adjacent end of the block next inadvance, and car-carried apparatus including a cab signal controlled bythe coded current flowing in the track rails in advance of the vehiclecarrying such car-carried apparatus.

16. In an absolute-permissive-blocl; signaling system, the combinationwith a railway track end of the block and said code responsive meansbeing capable of manifesting the reception of any one of a plurality ofcodes each consisting of a plurality of current impulses distinctivefrom the current impulses of any other code and being constructed tocontinuously manifest a code even though the code is intermittentlyabsent for time periods each period of which is long enough to allow acomplete code consisting of a plurality of current impulses to betransmitted in the opposite direction through the track rails,synchronously operated contacts at the two ends of each block foralternately connecting the code creating means and the code responsivemeans across the rails at its ends of the block in such synchronousrelation with the operation of the contacts at the opposite end of theblock that the code responsive means at the two enw of the block arealternately controlled by the Code creating means at the opposite end ofthe block, said contacts operating sumciently slow to allow a completecode comprising a plurality of current impulses to be transmitted duringeach closure of such contacts, means for controlling each code creatingmeans by the code responsive means at the adjacent end of the block nextin advance, and signals at each end of the block for governing themovement of traffic into that end of the block controlled by theassociated code responsive means.

1'7. In an absolute-permissive-block cab signaling system, thecombination with a railway track divided by insulating joints intoblocks, code responsive means at each end of each block governed throughthe rails of such block by code creating means located at the oppositeend of the block, said code responsive means being capable ofmanifesting the reception of any one of a plurality of codes eachconsisting of a plurality of current impulses distinctive from thecurrent impulses of any other code and being constructed to continuouslymanifest a code even though the code is intermittently absent for timeperiods each period of which is long enough to allow a complete codeconsisting of a plurality of current impulses to be transmitted in theopposit direction through the track rails, synchronously operatedcontacts at the two ends of each block for alternately connecting thecode creating means and the code responsive means across the rails atits end of the block in such synchronous relation wtih the operation ofthe contacts at the opposite end of the block that the code responsivemeans at the two ends of the block are alternately controlled by thecode creating means at the opposite end of the block, said contactsoperating sufiiciently slow to allow a complete code consisting of aplurality of current impulses to be transmitted during each closure ofsuch contacts, means for controlling each code creating means by thecode responsive means at the adjacent end of the block next in advance,and car-carried apparatus including a cab signal controlled by the codedcurrent flowing in the track rails in advance of the vehicle carryingsuch car-carried apparatus.

18. In an absolutepermissiveblock cab signaling system, the combinationwith a railway track divided by insulating joints into blocks, coderesponsive means at each end of each block governed through the rails ofsuch block by code creating means located at the opposite end of theblock, said code responsive means being capable of manifesting threception of any one of a plurality of codes each consisting of aplurality of current impulses distinctive from the current impulses ofany other code and being constructed to continuously manifest a codeeven though the code is intermittently absent for time periods eachperiod of which is long enough to allow a complete code consisting of aplurality of current impulses to be transmitted in the oppositedirection through the track rails, synchronously operated contacts atthe two ends of each block for alternately connecting the code creatingmeans and the code responsive means across the rails at its end of theblock in such synchronous relation with the operation of the contacts atthe opposit end of the block that the code responsive means at the twoends of the block are alternately controlled by the code creating meansat the opposite end of the block, said contacts operating suflicientlyslow to allow a complete code consisting of a plurality of currentimpulses to be transmitted during each closure of such contacts, meansfor controlling each code creating means by the code responsive means atthe adjacent end of the block next in advance, and a wayside signal ateach end of such block for governing the movement of trafiic into suchblock from that end controlled by the associated code responsive means.

19. In an absolute-permissive-block signaling system, the combinationwith a railway track divided by insulating joints into blocks, coderesponsive means and code creating means at each end of each block, saidcode responsive means being governed through the rails of such block bythe code creating means located at the opposite end of the block andsaid code responsive means being capable of manifesting the reception ofany one of a plurality of codes each consisting of a plurality ofcurrent impulses distinctive from the current impulses of any other codeand being constructed to continuously manifest a code even though thecode is intermittently absent for time periods each period of which islong enough to allow a complete code consisting of a plurality ofcurrent impulses to be transmitted in the opposite direction through thetrack rails, synchronously operated contacts at the two ends of eachblock for alternately connecting the code creating means and the coderesponsive means across the rails at its ends of the block in suchsynchronous relation with the operation of the contacts at the oppositeend of the block that the code responsive means at the two ends of theblock are alternately controlled by the code creating means at theopposite end of the block, said contacts being sufficiently slow toallow a complete code comprising a plurality of current impulses to betransmitted during each closure of such contacts, a directional stickrelay at each end of each block having a pick-up circuit and a stickcircuit each controlled by the associated code responsive means, meansfor controlling each code creating means by the directional stick relayof the adjacent end of the block next in advance, and signals at eachend of a block for governing the movement of trafiic into that end ofthe block controlled by the associated code responsive means.

20. The combination with a track section connected to adjacent track byinsulating joints, code creating and code responsive apparatus at eachend of said section, said code creating apparatus being constructed totransmit any one of a plurality of codes each code including a pluralityof impulses which distinguish in character from the impulses of anyother of said plurality of codes and said code responsive means beingconstructed to distinctively manifest the reception of any one of saidplurality of codes, double throw contacts at each end of said sectionoperated substantially in synchronism, and circuit wires including saidcontacts to alternately connect the cod creating and code responsiveapparatuses to the ends of said section in such a manner that the codecreating apparatus at one end is connected to the track section when thecode responsive apparatus at the other end is connected to the tracksection, the timing of said contacts being such that a complete codeconsisting of a plurality of current impulses is transmitted first fromone end to the other and then from the other to said one end of saidtrack section, and a signal at each end of said track section controlledby the associated code responsive means.

ROBERT M. PHINNEY.

